The present invention relates to the art of optical display systems. More particularly, the present invention relates to optical display systems having light valves and color displays.
In order to reduce the cost of light valve projection systems, it is common practice to employ an optical system with a single fast-responding light valve together with some sort of color selecting means (for example, a color wheel) operating in a sequential color mode. In such systems, the light valve rapidly displays monochrome frames of primary color information (generally three times faster than the normal refresh rate used for non-sequential systems.
For instance, to display a frame of a color image, the frame is displayed by projecting three rapid sub-frames, each sub-frame being of a single primary color. That is, to project one frame of a color image, a completely red image sub-frame, a completely green image sub-frame, and a completely blue image sub-frame are projected one after the other, very rapidly.
The rapid display of the monochrome sub-frame information on the light valve is synchronized with the colors passing through the color selecting means. This rapid succession of primary color images creates the impression of a single full color image in the mind of an observer due to the phenomenon of color persistencexe2x80x94the well-known fact that the human eye averages together information received over periods of a fifteenth of a second or so.
However, if the observer""s eye is not stationary relative to the image during the display on such a device (due to natural rapid saccadic motion of the eye, for example), the relative motion will cause the successive primary color images to fail to overlap perfectly on the viewer""s retina. The viewer will perceive incorrectly colored edges to bright objects under such circumstances, which will disappear when the relative motion ceases. This creates the annoying impression of a brief flash of color in situations where none was expected xe2x80x94a situation frequently referred to as xe2x80x9csequential color visual artifacts. xe2x80x9d The phenomenon is worst for two or more small white objects spaced apart horizontally and displayed against a black background. The natural saccades of a viewer""s eyes (which are most rapid in the horizontal direction) are frequently sufficient to cause strong and nearly continuous artifacts under such circumstances.
There is a need for a technique and an apparatus to alleviate sequential color artifacts.
The need is met by the present invention. According to one aspect of the present invention, an optical display system includes a lenticular array for focusing color light beams onto a plane forming a spatial mix of the colors of the beams and an optical translator for shifting the spatial mix of the colors of the plane.
According to another aspect of the invention, a method of displaying a frame of a color image is disclosed. A first sub-frame is projected, the first sub-frame having a spatial mix of primary colors and a second sub-frame is projected, the second sub-frame having a permutated the spatial mix of the primary colors.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in combination with the accompanying drawings, illustrating by way of example the principles of the invention.